As mentioned in the [API documentation](http://api.stackoverflow.com/1.1/usage/methods/questions-by-ids), you simply need to [pass in the `body=true` parameter](http://api.stackoverflow.com/1.1/questions/7406104?body-true) to get the body of the question.

In the [upcoming version of the API](https://stackapps.com/questions/2588/draft-specification-for-api-v2-0), you'll be able to use filters to specify what you want returned in advance.